Electrical cables which include at least one conductor core and at least one coating are well known.
Such cables present the disadvantage that their exterior surface has a high coefficient of friction, so that they are awkward to fit in internal sections of walls and ceilings or conduits, since when they come into contact with the surfaces they become stuck or difficult to pull, etc.
In order to overcome said difficulty, alternative materials such as vaselines and the like have been used to coat the exterior surface of the cable, thereby reducing the coefficient of friction.
In a complementary manner, guides of small diameter are sometimes used, one end of which is inserted through the cavity through which the cable has to pass and the other is attached to the end of the cable which must be inserted into the cavity. Thus, once the guide has emerged at the desired place it is pulled until the end of the cable appears again after having passed through the entire section.
In numerous fields of application, and in particular telecommunications, electric or fiber optic cables are inserted into ducts. There is therefore a need to minimize the coefficient of friction between cables and the inside walls of ducts.
In one solution, the core of the cable passes via a first extruder which applies a conventional sheath thereto i.e., a jacket and/or insulation, often made of polyethylene. The sheathed core then passes through a second extruder which applies a lubricant layer thereto, such as an alloy of silicone resin and polyethylene. The cable lubricated in that way then passes in conventional manner through a cooling vessel.
A second solution provides for an extruder to cover the core of a cable with a sheath. At the outlet from that extruder there is disposed a coating chamber for applying granules of material to the still-hot sheath, which granules are designed to become detached when the cable is inserted in a duct. Finally, the coated cable passes through a cooling vessel.
In both of these two prior solutions, it is necessary to interpose additional equipment between the extruder and the cooling vessel. That gives rise to a major alteration of the manufacturing line.
In addition, the equipment for depositing the lubricant must be very close to the sheath extrusion head since otherwise it is not possible to control the thickness of the sheath properly. In any event, the additional equipment occupies non-negligible space and such an arrangement is not favorable for control over the dimensions of the sheath.
Whatever the prior art method used, the manufacture and/or installation of said cables involves a considerable loss of time and an economic cost, since alternative materials are required.